fix: return empty patch type if there is no patch

[phbelitz]

When Connaisseur was done with the verification and returned an empty patch, the patch type was still set to JSONPatch. Kubernetes handled this regardless, but other tools like ArgoCD did not and threw an error. Connaisseur will now neither set a patch nor patch type and leave those fields empty, so it's compatible with other tools.

Fixes #1705

Checklist

• [x] PR is rebased to/aimed at branch develop
• [x] PR follows Contributing Guide
• [x] Added tests (if necessary)
• [x] Extended README/Documentation (if necessary)
• [x] Adjusted versions of image and Helm chart in Chart.yaml (if necessary)